Rope drum

ABSTRACT

A driven barrel of a winch device includes a closed cylindrical space (16) which is concentric with the barrel and accommodates a piston (17) which can move on an axis (12) from one end of the cylindrical space to the other and is in non-rotatable connection (19, 20) with the inside of the barrel. The axis (12) has screw threads (15) and the piston (17) has a center bore with screw threads meshing with the screw threads of the axis. The cylindrical space encloses a fluid and the piston (17) is given a leak from one side of the piston to the other. In order to stop the loaded rope unwinding from the barrel if the rotation speed of the barrel should increase over a certain value the leak is in the form of a canal (21) which accommodates a valve means including a valve housing and a valve body (22). The valve means stops the fluid flow over the valve body in one direction at a certain pressure drop over the valve body.

The present invention relates to an improvement in a driven barrel of awinch device to stop a rope to be unwound from the barrel when therotation speed of the barrel increases over a certain value in onedirection, whereat the driven barrel includes a closed cylindric spacewhich is concentric with the barrel and accomodates a piston, which canmove on an axis from one end of the cylindric space to the other innon-rotatable connection with the inside of the barrel, the axis havingscrew threads and the piston having a center bore with screw threadsmeshing with the screw threads of the axis, whereat the cylindric spacecontents a fluid and the piston is given a leak from one side of thepiston to the other side.

The invention particularly relates to a winding barrel in a hoistingmachine intended for sick or handicapped persons. In such cases thehoisting machine is disposed on a ceiling or a stand and by winding up acable or the like on its barrel a person in a harness is lifted. It isimportant that such machines are safe, compact and easily operated. Thebarrel is driven via a gearing, or some form of a belt driving and notinfrequently it happens that there is a machine or power supply failure.This may result in the barrel rotating freely counter to its windingdirection, such as to allow the cable to run either during hoisting orlowering, thus causing the person to fall to the floor or on to someother structure and possibly resulting in an injury. Limit switches areindeed often provided for the extreme positions for the barrel, forinhibiting the drive to the barrel, or stopping it from rotating, butdisturbances occur relatively often in these functions. There is alsothe ambition to make the drive means as small and as cheap as possible,which can lead to these means not standing up to overloads. In addition,a continuously driven barrel has no natural end positions and shouldoperation be incorrect, this could lead to the cable being wound up onthe barrel in the wrong direction of rotation. This would mean that thelimit switches function in the wrong order and wrong lift hights wouldbe obtained for the hoisting apparatus. The object of the invention isto stop the rotation of the barrel if the rotary speed in one directionshould happen to increase over a certain value.

An embodiment of the invention will now be described with reference tothe enclosed drawings.

FIG. 1 is a side view of a barrel of a winch and its driving motor.

FIG. 2 is a cross section through the barrel along the line A--A in FIG.1.

FIG. 3 is a longitudinal section through the barrel, showing thesupporting axis and driving gear along the line B--B in FIG. 2.

The hoisting device thus includes a barrel 1, which is driven to rotateby a motor 2 via a gear 3. The driving means are arranged at the rightend of the barrel 1. A belt is denoted by 4 and is wound up on thebarrel. The barrel is supported by bearings in end walls 5 of a housing6, which is supported by an elevated situated arm or is supported by aceiling. The barrel 1 thus is supported in its left end by the end wall7 and a bearing 8 and in its right end by the right end wall 5 via abearing 9 and a shaft pivot, which is extended from the right end wallof the barrel. The axis 12 extends through the barrel 1 and supports thebearing 8 of the barrel in the left end wall 7 of the barrel but isfixed in the left end wall 7 by a washer 13 and screws 14. The barrel 1can thus freely rotate in relation to the axis 12. The axis 12 isprovided with a helical thread 15 of suitable pitch. As can be seen thebarrel has a cylindrical space 16 between its two ends. A piston 17 isarranged within the cylindrical space 16. The piston runs within thecylindrical space to-and-from and is provided by a central bore havingthreads 18 of a pitch in correspondence with the form and pitch of thethreads 15. The piston 17 is further fixed to the barrel 1 by two keys19 in the inner side of the barrel and two keyways 20 on the outside ofthe piston, see FIG. 2. Keys and keyways are extended in thelongitudinal direction of the axis 12 and parallel with the axis 12,whereby the piston 17 will be non-rotatable in relation to the barrel 1and will move along the axis 12 because of the thread connection withthe axis when the barrel is rotated, see FIG. 3. The direction of themovement will depend on the rotary direction of the barrel 1 and thedirection of the helix form of the threads.

The space 16 is filled with a suitable fluid, preferably oil. A canal 21is bored axially through the piston 17 and the canal connects the leftside of the piston with its right side so that oil will flow through thecanal from the left side of the cylindric space to the right sidethereof and vice versa. When the barrel 1 is rotating, piston 17 willalso move in one of its two axial directions and oil will flow throughthe canal 21.

A ball 22 is located in the left end of the canal 21. To the right ofthe ball 22 in the canal there is a valve seat 23 against which the ballcloses the canal when the ball is forced to the right. The canal 21 hasa larger diameter than the ball and oil can pass in the space betweenthe outside of the ball and the inside of the canal. A spring 24 isplaced in the right end of the canal and forces the ball 22 away fromthe seat 23. A pin or the like prevents the ball 22 to be forced out ofthe canal 21 to the left. When the barrel is rotating in eitherdirection and the piston moves axially and rotates with the barrel, oilwill pass through the canal to the right when the piston moves to theleft and vice versa. The oil can flow freely in both directions throughthe canal 21 with one exception and that is to the right in FIG. 3 whenthe flow speed is increased over a certain value. Thus, when the flowspeed to the right reaches a certain great value, the pressure drop overthe ball will cause the ball to be moved to the right against the forceof the spring 24 and the bail will be pressed against the valve seat 23.The oil is hereby prevented to flow through the canal 21 and the piston17 can not be displaced axially, which will stop the rotation of thebarrel in the direction, which corresponds to the displacement of thepiston to the left in FIG. 3. The barrel is thus stopped by that theball stops the flow of oil through the canal 21 in the direction to theright in FIG. 3.

The described stop operation is used as an emergency stop for the barrelif, for instance, when lowering a person the driving motor or thetransmission to the barrel should collapse. The invention thus preventsthe barrel to assume a too high not controlled speed in one direction ofrotation. If this happens the rotation of the drum will be stopped.

It is possible to double the operation within the scope of theinvention, by either arranging a further canal and a ball but having anopposite operation mode so that the emergency stop will be in theopposite direction of rotation as to the one described or the ball canbe situated between two valve seats and two springs so that the ball canclose against one valve seat in both flow directions of the oil throughthe canal. The piston 17 also decides the two end positions for windingin and winding up of the rope 2. The piston thus stops the rotation ofthe barrel when the barrel has assumed its left position and rightposition respectively. A washer 25 is placed at the both end positionsin order to eliminate shearing between the screw threads and in order todecrease the thrust when the piston hits the inner end side of thebarrel in its end positions. These washers will give a smooth brakingfor the piston 17 when it reaches both end positions.

A best mode of the invention has been described above but within thescope of the invention further embodiments are possible. The placementof the cylinder space and the piston can be varied in relation to theplace on the barrel where the rope is wound up and thus it is possibleto arrange the cylindric space outside the barrel by forming anelongation of the barrel. The axis 12 and/or the barrel can be supportedin a different manner than described above. The connection between thepiston and the barrel can be designed by that a rod is extended insidethe barrel between its two ends and in parallel with the axis 12 andpasses through a hole in the piston whereby the rod is placed beside theaxis 12 and is fixed in the end walls of the barrel, so that the piston17 can not rotate in relation to the barrel 1 but move along the axis12. There are also other embodiments of valves which function asdescribed above. Thus, the valve body can have a different form than aball form. Other means than a spring can be used in resisting the valvebody to be pressed against the valve seat. The inventive idea accordingto the invention is that a pressure drop over the valve body at highflow speeds will cause the valve body to be pressed against the valveseat and thereby closing the valve and stopping the flow of oil.

I claim:
 1. Improvements in a driven barrel of a winch device to stop arope to be unwound from the barrel when the rotation speed of saidbarrel increases over a certain value in one direction, said drivenbarrel including a closed cylindric space which is concentric with saidbarrel and accommodates a piston, which is movable on an axis from oneend of said cylindric space to the other in non-rotatable connectionwith the inside of the barrel, said axis having first screw threads andsaid piston having a center bore with second screw threads meshing withsaid first screw threads of the axis, wherein said cylindric spacecontains a fluid and said piston is given a leak from one side to theother side of said piston, said leak being in the form of a canalthrough said piston in its axial direction, said canal accommodating avalve means including a ball freely movable in said canal and said ballcloses against a valve seat in said canal against the force of a springwhen the flow rate in a direction opposite to said spring force causes apressure drop high enough to overcome said spring force.
 2. The deviceas claimed in claim 1, wherein said non-rotatable connection comprisesan axial key way in either the outside of said piston or the cylindricalinner surface of said barrel and an axial key in the respective opposingsurface.
 3. The device as claimed in claim 1, wherein said two endpositions of the piston in said cylindric space have stops for saidpiston.